An efficiently tuned d-orbital occupation of IrO₂by doping with Cu for enhancing the oxygen evolution reaction activity

Abstract

Tuning Ir d-orbital occupation via doping Cu into the IrO2 lattice to prepare a highly efficient oxygen evolution reaction catalyst, Cu0.3Ir0.7Oδ.

Ultrasmall Ru/Cu‐doped RuO2 Complex Embedded in Amorphous Carbon Skeleton as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

“…It is clear that the binding energy of Ru (IV) in S‐400‐H is positively shifted by ≈0.3 eV compared with the S‐F‐400, indicating low electronic denisty at Ru sites. [14b,26] As displayed in Figure d, Cu 2p spectrum of S‐400‐H shows two deconvoluted peaks corresponded to high and low valence states of Cu, which is similar to the Cu‐doped IrO2 reported by Yang and co‐workers . While that of S‐F‐400 shows no apparent seperated peaks, which further demonstrates that there is no Cu‐doped into RuO 2 phase of S‐F‐400.…”

“…For a wide class of metal oxides, there is a good scaling relationship between the free energies of HO* and HOO* with a constant slope and an intercept of 3.2 (±0.2) eV. [26,28b] As shown in Figure S22 (Supporting Information), this scaling relationship also exists in our calculation models. Therefore, the overpotential can only be determined by the free energy of O* relative to HO*, which is denoted as Δ G (O*) − Δ G (OH*).…”

“…While that of S‐F‐400 shows no apparent seperated peaks, which further demonstrates that there is no Cu‐doped into RuO 2 phase of S‐F‐400. It is worth noting that the high valence state of Cu 2p is shifted toward higher binding energy state compared to that of CuO derived from S‐400, implying existence of the OCuORuO situation . In addition, inductively coupled plasma‐atomic emission spectrometric analysis indicated that the mass ratio of Ru to Cu in the complex is determined to be 16.72, which is consist with the atom ratio of 10.65 revealed by XPS survey result (Figure S4, Supporting Information).…”

OER activity manipulated by IrO6 coordination geometry: an insight from pyrochlore iridates

“…As our previous investigation on the Cu21 doped IrO 2 , when the Cu replace the Ir site in IrO 2 gives rise to a distortion of the IrO 6 coordination due to a strong Jahn-Teller effect of CuO 6 , which further influence the electronic structure of Ir site in particular changes the distribution of 5d electrons. The hollandite structure of K x  =  0.25 IrO 2 24 also exhibits better OER activity than IrO 2 , and its IrO 6 coordination is a distorted octahedron that strongly affect its electronic structure.…”

“…The preciousness and expensiveness of Ir limit its expansion in various applications. Thus, a vast research is being conducted in devotion to explore an advancement in OER activity to reduce Ir consumption based on iridate, such as binary or ternary oxides by doping other metal elements like Co19, Ni20, Cu21, Ru22 and Sn23, or oxides of new structure like hollandite24 and pyrochlore25. Even though enhancement of OER activity is acquired through addition of elements, still there is less understanding of structural aspects demonstrating variation in its activity when transition metals replace Ir sites in rutile IrO 2 or in the other novel crystal structure.…”